I had bought a set of the Pirellis/stock GT 18's for my V-6. When I upgraded to GT, I sold second set of Pirellis and bought stock size MPSS (based on quite a few reviews of how good they were).
They are 100 times smoother and quieter, but I wasn't really blown away by the change in handling. They also are downright horrible when temps get cold (below 40). Might be due to the stock size and I have bone stock base GT suspension, but at their price, I expected more.
86 Capri, turbo, 3.27's-12.66 @ 107.75
14 GT-Roush Phs 3, VMP 93 tune, Whiteline Sway Bars, Roush U/L Rear Control Arms, 18 X 9/10 Bullits with 295/255 NT05's